Field of the Invention
The present invention relates to piston engine fuels comprising mesitylene, pseudocumene and isopentane. These fuels may optionally include other components, particularly to modify characteristics as to octane rating, RVP, boiling point, cold start, smoke and deposits.
Description of the Prior Art
Three trimethylbenzene isomers are routinely found in the C9 aromatic stream of the refining process. They are often blended as aromatic hydrocarbons straight into the gasoline pool without separation, unless a unique need for separating the isomers is found, such as using mesitylene as a specialty solvent (e.g., as a developer for photopatternable silicones) or pseudocumene as a feedstock for trimellitic anhydride (TMA). Because the separation of the isomers is so challenging, and thereby commercially expensive, the processing cost often prohibits their consideration as a primary component for most aviation gasoline products.
U.S. Pat. No. 8,049,048 B2 entitled “Renewable Engine Fuel,” describes a two component aviation fuel comprised of 75-90% mesitylene and 15-30% isopentane. This patent uses the 1,3,5-trimethylbenzene C9 component that is the most difficult to separate, and fails to adequately leverage the less expensive C9 trimethyl aromatics components that contribute to high octane, primarily needed for high compression engines in the marketplace that consume aviation gasoline. U.S. Pat. No. 8,686,202 also discloses a high octane avgas combining mesitylene and isopentane.
Many other attempts have been made at devising a high-octane aviation gasoline starting from a base aviation fuel, some by combining alkylates up to 80%, as well as 5-15% of additional compounds to increase the octane and reduce the vapor pressure to aviation gasoline standards. See, for example, U.S. Pat. Nos. 8,628,594 and 5,470,358. One approach has involved the use of aromatic amines which may present a toxicity risk.